Television method and apparatus



April 14, 1936.

J. H. o. HARRIES 2,037,577

TELEVISION METHOD AND APPARATUS Filed Dec. 1, 1950 2 SheetsFSheet 1 AFig.1.

29 INVENTOR JOHN HENRY OWEN HARPJES,

&" ATTORNEY April 14, 1936. 1 O HARRlEs 2,037,577

TELEVISION METHOD AND APPARATUS Filed Dec. 1, 1930 2 Sheets-Sheet 2INVENTOR Patented Apr. 14,1936 w UNITED STATES PATENT OFFICE ApplicationDecember 1, 19:0. Serlal No. 499.32:

In Great Britain June 10. mo 1 18 Claims. (Cl. 11s-si The inventionrelates in general to the transmission and reproduction of pictures,scenes, views, images and the like by television and is concerned moreparticularly with forms of television apparatus in which a scanningpoint or beam is moved over the picture proportionally to electrical orelectrically controlled scannin forces. I

It is known that the definition of, and therefore the size of a picturetransmitted by television is proportional to the scanning speed and tothe width of the band of frequencies transmitted. Both the scanningspeed and the band width are seriously limited by practical require- 1ments and therefore it is exceedingly dimcult to transmit any but verysmall pictures.

It may be shownthat, because the human eye has only a very small pointof distinct vision in the total field of view, in a picture only thecentre of interest needbe very highly defined. The rest of the pictureneed only be of lower definition without detriment to the representationof the object portrayed.

The object of the present invention is to pro vide a method and meanswhereby such an unevenly defined picture may be employed in television.thus economizing the total amount of detail which need be transmittedand enabling a larger picture to be used than would otherwise bepossible.

' in accordance 'with the invention the electrical or electricallycontrolled scanning forces (hereinafter referred to as scanning forces)are arranged to have a suitable amplitude/time wave form so that thepicture is scanned more slowly, and therefore is greater in detail overthe center I of interest than elsewhere. For this purpose the speed ofthe scanning beam may be reduced as herein described in passing overthat part of the 40 picture which it is desired to emphasize orconversely in case it is desired to transmit pictures from a moving filmthe speed of the film relative to the scanning beam may be reduced whenthe beam is passing over that partof the picture 45 which it is desiredto emphasize, (the operative part of the wave being arranged to be themost useful portion).

Referring to the accompanying drawings in which like reference numeralsrefer to like parts: 50 Fig. 1 illustrates an example of wave shapeuseful in employing the invention.

Fig. 2 illustrates an additional wave form for the "purpose.

Fig. 3 illustrates one form of apparatus for pro- 55 .ducing the desiredwave forms.

- Figs. 4 and 5 illustrate other forms of apparatus for the purpose.

Fig. 6 illustrates another form of apparatus for the purpose in whichthe desired wave form may be produced by variations in the scanning ,5force itself.

Fig. 7 illustrates diagrammatically one form of circuit in which theinvention, may be employed for television.

Figs. 8 and 9' illustrate details of the apparatus 10 shown in Fig. 7.

As an example of the kind of wave form required, consider the case ofthe scanning forces in a cathode ray system. Two such forces are usuallyrequired, one rapidly oscillating to move 15 the jet, say 500 times asecond to produce the strips of the picture; and another slow framing"deflection at right angles to the above to produce the required numberof pictures per second.

It will be understood that the centre of interest go will usually be atabout the centre of the picture.

where the point or beam normally rests when the scanning current is atzero amplitude.

Concerning the above-mentioned rapidly oscillating wave, if this is ofsinusoidal form, as is 25 usual in the operation of a cathode raysystem, the current rate of change with time, and therefore the rate ofscanning, will be at its greatest at zero current. Therefore the picturewill be scanned at the fastest rate in the middle. But 30 the rate isrequired to be at the least here.

The present invention may however employ a wave for example, of the formy= (a sin w) sin 3 w) The wave is plotted in Fig. 1 of the accompanyingdrawings, the operating part being between A and B. I

The comparatively slow framing deflection is frequently arranged to belinear with time so as to spread the scanning lines evenly and so givean evenly defined picture. But in order to give a greater definitionover the centre of interest lying about the nnddle of the picture, inaccordance with the present invention, the time rate of change of thescanning forces must again be less over the centre of interest thanelsewhere. In Fig. 2 curve I represents the usual linear relationbetween the scanning force 12, with the time t, and curve 2 representsthe non-linear eflect desired in accordance with the invention.

The desired wave form may be generated by a plurality of coupledgenerators, each delivering a component of the desired-complex wave,which 86 would appear in a circuit to which the components are fed. Therelative characteristics of the individual components may be varied bysuit- I able adjustments to the generators or to the couplingbetween thegenerators. The generators may themselves be driven by a motor to act asa motor generator convertor. In Fig. 3 this is illustrated as applied totwo alternators 3, 4, and

a potentiometer 5 controls the relative strength and the two alternatorswould be coupled in anticurrent phase to produce the desired resultant 1=a sin w= sin 3w As an alternative the desired wave may bade;-

rived from a periodic variation of the circuit con-;

. stants, e. g., resistance or capacity.

In Fig. 4 a cam 10, is'rotated at a constant speed by any suitablemeans; one end of a fol lower or rod ll, slidably mounted in bracketsI2,

is held in contact with thecam profile by a spring I3, and on theopposite end of the follower H, is a contact which slides over aresistance M.

The terminals of the external circuit are con:

nected to one end of the resistance l4, and to the follower contactrespectively. As the cam I8 rotates the contact slides over theresistance It,

and causes a periodic variation of the'resistance in the externalcircuit. The cam profile is of such a shape as to cause the resistanceand therefore the current in the external circuit to vary pe-'riodically as shown by the curve Fig. 1.

In the arrangement illustrated in Fig. 5, a disc 15 is steadily rotatedby any convenient means, and a resistance wire or strip I6, is arrangedaround its edge; one end I! of said wire being connected to the externalcircuit, the other end is free. An electrode I 8, rubs on the wire, andis connected to the other terminal of the external circuit. Theresistance I9 is connected between the external circuit, where the end II of the wire l6 joins it, and the middle point of the wire l6. As thedisc l5 revolves it will'be realized that a periodic variation of thecircuit resistance between the end I! of wire l6 and the electrode l8,will take place; further, the resistance l9 will act as a shunt and willcause the total circuit resistance to drop when the electrode l8 passesover or near its point of junction with the wire Hi.

It is evident that the resulting resistance and therefore currentvariation in the external circuit will be of the type of curve 2 shownin Fig. 2. The arrangement shown in Figs. 4 and 5 may advantageously beused together to respectively produce co-operating scanning forceshaving the wave forms illustrated in Figs. 1 and 2. In such case, thecam l and disk l may be driven by a common prime mover.

Very many variations of these arrangements will suggest themselves tothose skilled in the art.

A further series of arrangements will consist 01' devices wherein thecircuit constants change with difierent magnitudes of the scanningforces; in this -manner a sine wave, or transient force, may be made toproduce the desired wave form.

One example consists of a pair of triode valves in push-pull amplifierarrangement. The valve grids are biased so that the'lower values of asine wave impressed on the grids are partially suppressed, the peaksbeing reproduced normal- 1y, resulting in an output wave form similartoFig. 1.

- A second example is where a series of devices (e. g. diode or triodevalves orother relaying devices) are biased so as to come intooperationin shunt or series in a circuit at difl'erent values of the input volts,hence varying the current output wave form, either by their varying loadon the circuit or by switching in or out additional apparatus, e. g.,capacities, etc.

The operation of mechanical relays may be delayed in order to act at theright instant by means of oil dash-pot apparatus or the like.

In Fig. 6, the present invention is applied to a known form of apparatuswherein the potential across the plates of a condenser, which is chargedthrough a constant current device, is utilized to give the deflectingforce to a cathode'ray tube.

The condenser 20 has in parallel therewith the deflecting plates 2| ofthe cathode ray tube, and a relay operated short circuiting switch 22,and a diodevaive 23 biased'by a battery 24. In series with all thesedevices, and in series with a diode 25 and. triode 26 (which are inparallel with each other) is a battery 21. Resistance 28 is merely toprovide a path for the D, C. plate current to diode25 and triode 26 whenthe relay switch 22 is open. 'I'hegrid of triode 26 is connected to abiasing battery 29 and the other terminal of said battery is connectedto the top of the condenser 20 at 30. The apparatus described may beemployed in a. television system when periodic impulses are used as thescanning force for framing purposes, said periodic impulses being causedto momentarily close the switch 22 between the transmission ofsuccessive pictures. The operation of this circuit is as follows:-

On the condenser 20 being periodically short circuited it is discharged.When the switch 22 is opened the said condenser 20 commences to chargeup from battery 21 through the diode 25, which is arranged to pass aconstant current. The diode 23 and triode 26 are respectively biased sothat they do not operate at the initial values of the rising voltageacross the condenser 20 as it commences charging up.

From known theory this voltage rises linearly with time due to theconstancy of the charging current. This condition holds until thevoltage reaches the value a: on the curve in Fig. 2, (where u mayrepresent the voltage across the condenser 20, and 1., time as before,)when the voltage on the plate of diode 23 is suflicient to overcome theeii'ect of the biasing battery 24, and the diode 23 becomes conductingto an extent which increases over a short interval of time. During thistime a portion of the current from battery 21 is deflected from thecondenser 20, and the voltage across this condenser 20 does not increaseas rapidly as heretofore. This efiect is shown in Fig. 2 over the partof the curve between a: and 3/. At y the voltage across the condenser 20and on the grid of the triode 26 becomes suflicient to overcome theeffect of the bias battery 29, and the plate circuit of the triode 28commences to conduct, thus increasing the charging current and causingthe curve in Fig. 2, to bend upwards until the condenser is again shortcircuited and discharged by switch 22, when the cycle of operationsagain continues. The result is therefore the production of the desiredcurve as in Fig. 2.

A triode with the grid suitably biased and connected to-point 30 may besubstituted for the diode 23. The increasing current through this triodeafter the point 3 on the curve, (Fig. 2) will partially counteract theeffect of the triode 26 in raising the curve, and must be allowed for indesign. v

The same general principle of employing differently biased tubes, asexplained her may be employed to change the time rate of change of aninput wave over part of its curve.

By altering'the scanning wave form from either the transmitter or thereceiver, (by means of known remote control devices) the position of thehighly defined part of the image may be moved over the remainder of theimage. For instance, in the apparatus illustrated in Fig. 3, therelative (mechanical) phase and excitation of the two alternators may bevaried, or in the apparatus shown in Fig. 4 the cam may be altered oradjusted.

For the better understanding of the invention an example of oneapplication of the present invention to a cathode ray television systemis diagrammatically illustrated in Figs. 7, 8 and 9.

In Fig. 7 a cinematograph film 3| is fed past a cathode ray scanner 32and photo-electric cell 33. Scanner 32 includes a cathode 4| and anode42 connected in series with a battery 43 in the usual manner to producea jet of cathode rays 46, which impinge on the fluorescent screen 34.Light rays from the consequent light spot on the fluorescent screen 33are focussed by lens 35 onto the film 3|. The film is moved past thecell 33 and scanner 32 by means of the sprockets 36 which are bothmechanically coupled to shaft 31. Shaft 31 is driven through a gearmechanism 36 by a prime mover 39. The prime mover 39 also drives thegenerators 3, 3 which supply scanning currents to the circuit l, aspreviously illustrated in Fig. 3. Circuit 1 is connected to thedeflecting plates 44 of the transmitting scanner 32, and also to thecorresponding plates 45 of a receiving cathode ray scanner 46.

The receiving scanner 40 consists of a cathode 41 and anode 36 in serieswith a battery 49 in the usual manner to produce a jet of cathode rays56, which impinge on the fluorescent viewing screen 5| The jet 50 isdefiectable by potentials applied to the plates 2| and 45. The intensityof the light spot produced on the viewing screen 5| by the impact of thejet 50 is controlled, also in known manner, by the potentials applied tothe electrode 52.

The picture currents from the photo-electric cell 33 are transmittedthrough lines 53 and amplifier 54 to the cathode 41 of the receivingscanner 46 and to the control electrode 52 therein.

Plates 2| of the receiving scanner 40 are connected across the condenser26. Condenser 20 is discharged and charged up once for every picturetransmitted from the film 3| by means of the apparatus 23, 24, 25, 26,21, 28, 29 (as illustrated previously in Fig. 6) the triode valve 55being arranged to act as the short 'circuiting switch 22 shown in Fig.6.

The lines 56 and battery 5] are connected to switch arm 58 and contact59. Switch arm 58 is fastened to sprocket 36 so that contact is made to59 between the transmission of each picture on the dim 3|. A highresistance 61 and battery 69 maintain the grid of the triode 55 atasumciently negative potential to make the plate circuit virtuallynon-conducting when contact 56, 59 is open.

The gear mechanism 36 is shown in greater detail in Figs. 8 and 9'.

In Fig. 8 the pinion 66 is in mesh with a gear wheel 6 I rotated at aconstant speed by the prime mover 39 (in Fig. 7) said pinion alsoengaging teeth in an eccentrically mounted gear wheel 62, mounted on theshaft 31.

It will be seen from the drawings (Fig. 9) that the configuration of thegear wheel 62 is such that though theperipheral speed of said gear wheel62 is constant, the speed of rotation of the shaft 31 will vary inaccordance with the configuration of the gear wheel 62.

The pinion 60 is supported by a member 63 secured to a collar looselymounted on shaft 31, said member 63 being angularly adjustable by meansof a pinion 65 engaging teeth 66 on the member 63, said pinion beingrotatable for this purpose by any convenient'means, or by known remotecontrol means (not shown); so that the position of pinion 60 may beangularly adjusted in relation to gear wheels 6|, 62, thus permittingthe variations in speed of shaft 31 in relation to the speed of primemover 39 to be adjusted in phase or angular relation for the purposesherein defined.

The operation of the apparatus shown in Figs. 7, 8 and 9 is as follows:1

The film 3| at the transmitter and the fluorescent viewing screen 5| atthe receiver are scanned synchronously. At the transmitter the scanningmovement is provided by the combination of the movement of the jet ofcathode rays 46 over the fluorescent screen 34 by the potentials on theplates 44, and the movement of the fllm 3| by the sprockets 36 past thescreen 34 in the direction at right angles to the direction of scanningby the jet 46.

At the receiver the scanning is performed by the combination of themovement of the jet 56 over the fluorescentscreen 5| by the potentialson the plates 45, and the movement of the jet 56 in the direction atright angles to this movement by the potentials on the'plates 2-|.

At the transmitting scanner the light from the point of impact of thejet 46 on the fluorescent screen 34 is focussed by means of the lens 35onto the film 3| and, after passing through the film, impinges on andoperates the photo-electric cell 33. The instantaneous value of thecurrent given by the cell 33 is proportional to the density of the film3| at the point being scanned at that instant, and the current from thecell 33 is transmitted by lines 53 and amplifier 54 to the controlelectrode 52 of the receiving scanner 40. Therefore the brightness ofthe spot of light on the fluorescent viewing screen 5| at any instant isproportional to the light and shade of the point of the film 3| which isbeing scanned at that instant. Therefore, according to the usual theoryof the operation of television apparatus, images of pictures on the film3| at the transmitter will appear on the fluorescent viewing screen 5|at the receiver, provided that both are synchronously and similarlyscanned.

In the example-illustrated in Fig. 7 synchronism and similarity ofscanning are obtained as follows:

Since theoutput of the generators 3, 4 is connected to both the plates44 of the transmitter scanner 3!, and to the plates 45 of the receiver,in velocity at any instant, and, as previously explained, will causethe centre of interest of the picture transmitted to be scanned ingreater detail than elsewhere.

Referring to the slower, or framing", deflection of the jet in thereceiving scanner 40, this is provided by the non-linear charging of thecondenser 20 across which the plates 2| of the scanner 40 .areconnected. This, as previously explained, will cause the centre ofinterest of the pictures to be more closely scanned than elsewhere. Thiscondenser is discharged between the transmission of each picture on thefilm 3i by means of the contact arm 58 and contact 59 switching in aheavy positive bias from battery 51 onto the, grid of the triode thusovercoming the negative bias from battery 39, and causing the platecircuit of said triode 53 to become momentarily highly conducting andhence providing a discharge path for the condenser 20.

It is necessary that the corresponding "framing" movement of the film 3|past the scanner 32 should also be at a slower rate over the centre ofinterest of each picture on the film 3| than elsewhere. This is providedby the uneven velocity of ,drive to the sprockets 36 given by the gearmechanism 38, as explained heretofore. And thus, by operation of gearthe changes in film speed may be adjusted to correspond with the changesin speed of movement of the cathode ray 50 induced by change inpotential of plates 2|. It is obvious that any other appropriatevariable speed drive may be used in place of the device 38.

Various refinements which will suggest themselves to those skilled inthe art may be added without departing from the scope of the invention.As an example, the special scanning wave forms, the production of whichis the object of the present invention, may be modified over a part, oronly be used over part, of each picture scanned. This may beaccomplished, for instance, in the case of the application shown in Fig.'7, by arranging a further series of contact arms and contacts on theprime mover or sprocket shafts, to alter the point on the potentiometer5 to which the generator 3 is connected, or by cutting out the generator3 altogether.

By this means the slow scanning of the mid section of each picture,-i.e., from one side to the other thereof or from top to bottom,-- may beeliminated at the edges of said section so as to take place only at thecentre of the picture, thus emphasizing the real centre of interest andsubordinating the entire border.

Furthermore it will be seen that by adjusting the speed of the primemover 39 inFig. 7 the speed of transmission and reception of thesuccessive pictures on the film 3| and the image frequency to betransmitted by lines 53 and amplifier 54 may be adjusted, at will, tosuit the conditions under which the operation is being conducted andwithout disturbing the synchronous cooperation of all the operatingparts.

In order to avoid the transmission of a complex synchronizing wave fromthe transmitter to receiver (e. g. by circuit 1, -a sinusoidal wave maybe employed and converted at the receiver by suitable means to thedesired wave form. For instance, in Fig. '7, in cases wherein the primemover 39 consists of a synchronizing motor, instead of circuit 1 beingconnected to plates 45 in the receiving scanner 40, a sinusoidal cur.rent driving the prime mover may be transmitted to. the receiver andcaused to drive a prime mover similar to 39 which drives generators suchas 3, l in Fig. 3 to produce a special scanning wave identical with thatin circuit 1 for application to the plates 45 of the receiving scanner40. In referring herein to transmission of pictures etc., I mean torefer to methods or apparatus either for the sending or receivingthereof in accordance with the invention or two systems which employ theinvention both in sending and in receiving.

It will be understood that the foregoing description of circuits anddevices is simply to illustrate and not to restrict my invention whichmay be embodied in many different forms of apparatus and circuits. I donot intend to limit my invention except as defined in the appendedclaims.

I claim:

1. Television apparatus comprising means for producing a scanning beam,means for producing a force in wave form, the waves of said force havinga retarded rate of change adjacent zero amplitude, means for applyingsaid force to the scan ning beam to effect movement thereof across anobject to be scanned to scan a portion thereof at a slower rate thanthat at which the remainder is scanned.

2. Television apparatus comprising means for producinga scanning beam,means for producing a force in wave form, the waves of said forcehavinga retarded rate of change adjacent zero amplitude, means forproducing another force of increasing magnitude, means for applying saidforces to the scanning beam to effect movement thereof across an objectto be scanned to scan a portion thereof at a slower rate than that atwhich the remainder is scanned.

3. Television apparatus comprising means for producing a scanning beam,means for producing a force in wave form, the waves of said force havinga retarded rate of change adjacent zero amplitude, means for applyingsaid force to the scanning beam to effect movement thereof in a pathacross the object to be scanned to scan a portion thereof at a slowerrate than that at which the remainder of the object is scanned, andmeansto effect relative movement of said beam and object transversely to saidpath.

4. Television apparatus comprising means for producing a scanning beam,means for producing a force in wave form, the waves of said force havinga retarded rate of change adjacent zero amplitude, means for applyingsaid force to the scanning beam to effect movement thereof in a pathacross the object to be scanned to scan a portion thereof at a slowerrate than that at which the remainder of the object is scanned, andmeans to effect relative movement of said beam and object transverselyto said path at a periodically varying rate of speed.

5. Television apparatus which comprises means for producing a scanningbeam, means for producing a wave form scanning force and applying thesame to said scanning beam to effect vibration thereof along a straightpath, and means for modifying said scanning forces to retard the timerate of change of position of said scanning beam over the centralportion of its path.

6. Television apparatus which comprises means for producing a scanningbeam, means for producing a wave form scanning force and applying terestof the object is scarmed'than during the scanning of the remainder ofthe picture. ,7. Television apparatus comprising means for producing ascanning beam, means for producing 4 a wave form force approximatingthat given by the expression a y=a sin W lin 3w and means for applyingsaid force to said beam to efiect vibration thereof.

8. Television apparatus comprising means for producing a scanning beam,a plurality of generators having different outputs and coupled toproduce a wave form approximating that given by the expression a y=a sinwsin 3w and means to apply said force to the scanning beam to effectvibration thereof.

9. Television apparatus comprising means for producing a scanning beam,a plurality of generators having difierent outputs and coupled toproduce awave form force having a retarded rate .of change adjacent zeroamplitude, and means for applying said force to said beam to effectmovement thereof corresponding to changes in amplitude of said force.

10. Television apparatus comprising means for producing a scanning beam,a plurality of generators having different outputs and coupled toproduce a wave form force having a retarded rate of change adjacent zeroamplitude, means for applying said force to said beam to efifectmovement thereof corresponding to changes in amplitude of said force,and means to effect relative movement of the object to be scanned andsaid versely to the path of one beam, translating the beam transverselyof the said first movement at a periodically varying rate of speed.

11. Television apparatus comprising means for producing a scanning beam,a circuit for produc-; ing ai'force proportional to a voltage ofprogressively increasing magnitude, means in said circult responsive tovariations in the magnitude of said voltage for varying the constants ofthe circuit to vary the rate of change of magnitude of said voltage, andmeans for applying said force to said scanning beam to effect movementof the same corresponding to the change in magnitude of the force.

12. Television apparatus comprising means for producing a scanning beam,a circuit for producing a force proportional to a voltage ofprogressively increasing magnitude, means for applying said force tosaid beam to effect movement thereof corresponding to changes inmagnitude of the force, and thermionic devices in said circuit biased tooperate at different values of said voltage for varying the rate ofchange of magnitude of said force. a v

13. Television apparatus comprising means for producing a scanning beam,a. circuit for producing a force of progressively increasing magnitude,

' the same to said scanning to eifect vibration'thereof along a.straight path, and means arotatable resistor, a contact member, means torotate said resistor to vary the resistance of said circuit, a secondresistor associated with said first resistor to retard the rate ofchange of re-' sistance during a predetermined interval, meansforapplying the force to said scanning beam .to effect movement thereofcorresponding to the change in resistance of said circuit.

14. Television apparatus comprising means'to produce a pair of scanningbeams, means for producing a wave form force having a slower rate ofchange adjacent zer o amplitude than elsewhere, means for applying saidforce tosaid scanning beams to eifect vibration thereof along straightpaths, means to advance the object to be scanned transversely to onebeam at a periodically varying rate of speed, means for producing aforce of progressively increasing magnitude proportional to the extentof movement of said object, and means for applying said force to thesecond beam to effect movement thereof normal to its vibrating movementat the same rate of movement as'said object.

15. Television apparatus comprising means to produce a pair of scanningbeams, means for producing a force in wave form, the waves of said forcehaving a retarded rate'of change adjacent zero amplitude, means forapplying said force to second beam to effect movement thereof normal tothe movement effected by the first force.

16. The method of transmitting an image of an object by television whichcomprises vibrating a pair of scanning beams along straight paths,moving the object to be scanned transresulting light various into imagecurrents, causing these image currents to modulate the second beam,moving the path of the second beam transversely in proportion to themovement of the object, and retarding the rate of movement of thescanning beams and object during the interval of time during which thecenter of interest of the object is being scanned.

17. The method of scanning an object for transmission of an imagethereof by television according to which a scanning force is produced inwave form, the waves of said force having a retarded rate of changeadjacent zero amplitude, and is applied to a scanning beam to effectmovement thereof across the object to scan the center of interestthereof at a slower rate than that at whicl'rthe remainder is scanned.

18. A method of television scanning which includes causing a spot oflight to traverse a subject in such a manner that the instantaneousangular velocity of the spot is a minimum at the center of the traverse,and a maximum at the extremities of the traverse.

JOHN HENRY OWEN HARRIES.

5 CERTIFICATE or CORRECTION.

Patent to. 2,037,577.

JOHN HENRY OWEN HAERI s.

7 It is" hereby certified that error appears in the printedspecification of the above numbered -patent requiring correction asfollows: Page 2, first column, -line;.25, in the equation, strike outthe equal sign second occurrence, and insert instead a minus sign; andthat the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case inthe'Patent Office.

Signed and sealed this 19th day of May, A. p'. 1936.

Leslie Frazer [Seal) Acting Commissioner of Patents;

April 14, 1936.

